1. Field of Invention
This invention relates to measurements of monocyte CD163, a monocyte/macrophage-specific scavenger receptor for hemoglobin-haptoglobin complex, mean fluorescence intensity and frequency measurements in blood which is an important surrogate marker for clinical management of HIV-1 infected individuals. This marker may be used to predict disease progression, viral load and changes in viral load, and may be important in diagnosis and or risk assessment relative to CNS and other neurological manifestations of HIV infection.
2. Description of Related Art
Monocytes are a heterogeneous population of cells capable of differentiation into a variety of mature cell types including different subsets of macrophages, myeloid endritic cells and osteoclasts. The invention provides that alterations in monocyte populations in human immunodeficiency virus type 1 (HIV-1) infection, correlate to expression of two cell surface markers, CD16 and CD163. While all monocytes express CD14, a lipopolysaccharide (LPS) receptor, (Ziegler-Heitbrock H W, Passlick B, Flieger D. The monoclonal anti monocyte antibody My4 stains B lymphocytes and two distinct monocyte subsets in human peripheral blood. Hybridoma 1988, 7:521-527.), the less frequent CD16+ monocyte subset is considered more mature, with characteristics similar to mature macrophages (Ziegler-Heitbrock H W, Fingerle G, Strobel M, et al. The novel subset of CD14+/CD16+ blood monocytes exhibits features of tissue macrophages. Eur J Immunol 1993, 23:2053-2058.). Increased frequency of CD14+/CD16+ monocytes in the setting of HIV-1 infection have been observed by several groups (Allen J B, Wong H L, Guyre P M, Simon G L, Wahl S M. Association of circulating receptor Fc gamma Rill-positive monocytes in AIDS patients with elevated levels of transforming growth factor-beta. J Clin Invest 1991, 87: 1773-1779; Locher C, Vanham G, Kestens L, et. al. Expression patterns of Fc gamma receptors, HLA-DR and selected adhesion molecules on monocytes from normal and HIV infected individuals. Clin Exp hnmuno/1994, 98: 115-122; Thieblemont N, Weiss L, Sadeghi H M, Estcourt C, Haeffner-Cavaillon N. CD14lowCD16high: a cytokine-producing monocyte subset which expands during human immunodeficiency virus infection. Eur J Immuno/1995, 25:3418-3424; Pulliam L, Gascon R, Stubblebine M, McGuire D, McGrath M S. Unique monocyte subset in patients with AIDS dementia. Lancet 1997, 349:692-695.). Further, while HIV-1 infected patients naive to highly active antiretroviral therapy (HAART) have expanded CD16+ monocytes and express higher levels of proinflammatory cytokines, they also show increased levels of the antiinflammatory cytokine, ILIO (Amirayan-Chevillard N, Tissot-Dupont H, Capo C, et aJ. hnpact of highly active antiretroviral therapy (HAART) on cytokine production and monocyte subsets in HIV infected patients. Clin Exp hnmunol 2000, 120:107-112.). While it was not determined in that study which monocyte subset (CD14+/CD16+ or CD14++/CD16) was responsible for ILIO production, the results suggest that there may be an association between the CD16+ monocyte subset and IL10 expression. Comparable to the TH1 versus TH2 cytokine profiles expressed by T cells, macrophages can exhibit analogous polarization. While the proinflammatory, IL12 producing Macrophage-1 are involved in antigen presentation and memory T cell activation, IL10 producing, alternatively activated macrophages, MΦ-2, are primarily involved in housekeeping functions, i.e. phagocytosis, tissue remodeling and immune suppression. Both populations have their appropriate functions; however, polarization to a MΦ-2 phenotype could have important immune consequences in the setting of HIV-1 infection by adversely affecting the ability of the host immune system to adequately control virus as well as other opportunistic pathogens implicated in AIDS pathogenesis. It is likely that alterations in monocyte populations promote a TH2 cytokine shift and contribute to the pathogenesis of HIV infection.
Expression of CD163, a scavenger receptor for hemoglobin-haptoglobin (hg-hp) complex, is reportedly exclusive to monocytes and specific tissue macrophages in humans and has been used to phenotypically identify Mt-2 (Zwadlo G, Voegeli R, Osthoff K S, Sorg C. A monoclonal antibody to a novel differentiation antigen on human macrophages associated with the downregulatory phase of the inflammatory process. Exp Cell Biol 1987, 55:295-304; Sulahian T H, flogger P, Wainer A E, et al. Human monocytes express CD163, which is upregulated by IL-10 and identical to p155. Cytokine 2000, 12:1312-1321; Lau S K, Chu P G, Weiss L M. CD163: a specific marker of macrophages in paraffinembedded tissue samples. Am J Clin Patho/2004, 122:794-801; Nguyen T T, Schwartz E J, West R B, Warnke R A, Arber D A, Natkunam Y. Expression of CD163 (Hemoglobin Scavenger Receptor) in Normal Tissues, Lymphomas, Carcinomas, and Sarcomas Is Largely Restricted to the Monocyte Macrophage Lineage. Am J Surg Patho/2005, 29:617-624.). Considering the significance of macrophages in HIV-1 infection and disease progression and the potential role of MΦ-2 in skewing the host immune response to an anti-inflammatory phenotype, peripheral blood from HIV-1 infected and seronegative individuals was examined for alterations in CD163+ monocyte subsets and assessed their correlation with viral load and AIDS progression. While CD163 expression is associated with the macrophage Φ-2 phenotype, it is unclear if CD163+ monocytes are a circulating form of the MΦ-2. In support of this notion IL10 secreting monocytes have recently been demonstrated to exhibit an increased frequency of CD163 expression (Prasse A, Germann M, Pechkovsky D V, et al. IL-10-producing monocytes differentiate to alternatively activated macrophages and are increased in atopic patients. J Allergy Clin Immuno/2007, 119:461 171.). Since CD16 expression on monocytes suggests a more mature macrophage phenotype, it is possible and even likely that the CD163+/CD16+ monocytes are circulating forms of the MΦ-2 or are predisposed to further differentiate into the MΦ-2.
HIV-1 dementia complex (HIVD) affects approximately 10% of adults and almost all children infected with HIV-1 with acquired immunodeficiency syndrome (AIDS). HIV encephalitis (HIVE), the pathology of HIVD, is characterized by an accumulation of perivascular macrophages, multi-nucleated giant cells, and nodular lesions with areas of focal necrosis and white matter thinning (Rostad S W, Sumi S M, Shaw C M et al. Human immunodeficiency virus (HIV) infection in brains with AIDS-related leukoencephalopathy. AIDS Res Hum Retroviruses. 1987; 3:363-373; 2. Pumarola-Sune T, Navia B A, Cordon-Cardo C et al. HIV antigen in the brains of patients with the AIDS dementia complex. An Neurd. 1987; 21:490-496; 3. Budka H, Costan G, Cristina Set al. Brain pathology induced by infection with the human immunodeficiency virus (HIV). A histological, immunocytochemical, and electron microscopical study of 100 autopsy cases. Acta Neuropathol (Berl). 1987; 75: 185-198.). The Trojan Horse' model was originally proposed, where circulating HIV-1 infected macrophages seed the central nervous system (CNS) early in HIV-I infection with transmission to other cells within the CNS compartment, leading to neuronal loss and CNS dysfunction (Meltzer M S, Skillman D R, Gomatos P J et al. Role of mononuclear phagocytes in the pathogenesis of human immunodeficiency virus infection. Annu Rev Immunol. 1990; 8:169-194.). An alternative hypothesis is that the initial productive infection in the CNS is cleared by the immune system, with a second invasion in the setting of AIDS. This model was proposed by Pullam et al. (Pulliam L, Gascon R, Stubblebine M. et al. Unique monocyte subset in patients with AIDS dementia. Lancet. 1997; 349:692-695.), where increased levels of CD16+ monocytes were observed in circulation in AIDS, particularly in the setting of dementia. Based on the activation of this circulating monocyte subset, increased invasiveness of these cells was proposed to playa role in the pathogenesis of HIVD. Previously, we identified two populations of activated MPs in the CNS of patients with HIVE (Fischer-Smith T, Croul S, Sverstiuk A E et al. CNS invasion by CD14+/CD16+ peripheral blood-derived monocytes in HIV dementia: perivascular accumulation and reservoir of HIV infection. J. Neurovirol. 2001; 7(6):528-41.). Recently, CD163, a monocyte/macrophage-specific scavenger receptor for hemoglobinhaptoglobin complex, was reported to be expressed in the CNS by perivascular macrophages but not by resident microglia in human brain. The inventors utilized this disparity in the expression pattern of CD163 by perivascular macrophages versus microglia to further characterize the mononuclear phagocytes (MPs) in the CNS in HIVE. Briefly, we found a significant number of CD163+ macrophages accumulating perivascularly and within the brain parenchyma in patients with HIVE. Many of the CD163+ cells observed in the parenchyma of patients with HIVE have a ramified morphology and likely represent CNS engraftment of perivascular macrophages that have migrated into the brain parenchyma and taken on microglial characteristics. The majority of CD163+ cells is also shown by co-localization studies to harbor productive HIV-1 infection and as such, is a significant source of virus in the CNS. Further, CD163 co-localizes significantly with CD16 in HIVE CNS. Here we show that uninfected and S1Vmac251 infected Rhesus macaques with and without SIV encephalopathy (SIVE) have alterations in peripheral blood monocyte activation/maturation markers by flow cytometry and this correlates with viral load and CNS disease.
All references cited herein are incorporated herein by reference in their entireties.